Yamaha RX-A1030 I Protect

[krustyone]

Hi all,

Normally fix TV's however this is the first amp I have worked on in the modern era....

The amp after resetting the protect, will power up until the speaker relays kick in after which it performs an immediate shutdown.

Checking the speaker terminals reveals -7.5volts on all terminals except for the Zone 2 channels.

All output transistors appear to be ok with no obvious shorts etc.

It looks like I have a floating ground somewhere however I'm just not sure where to start looking.

Any advice will be greatly appreciated.

The service manual link is https://elektrotanya.com/yamaha_rx-a.../download.html

[R_J]

Re: Yamaha RX-A1030 I Protect

Check your lower voltages, especially + and - 12 volts (page156) If one of those voltages is off it will upset the balance.
There are two sources for +&-12v check them both

Zone 2 may not be turned on so the relay for zone 2 speakers does'nt turn on. You would need to check the voltage before the relay contacts

[krustyone]

Re: Yamaha RX-A1030 I Protect

Thanks for that R_J.

I check both 12v supplies and they appear to be okay.

Doing some more checks around MAIN 1 and MAIN 2, I noted the positive and negative rails to output stages where around 55 volts in stead of 59.
Also - and + LB_L ate showing around 2 to 4 volts. Well short of the expected 59 volts.

I should also add that when the second relay kicks in after about 3 seconds, the 55 volts at the output stages progressively begins to fall although this has only happened once or twice when it sounds like 2 relays switch on.

After a couple of restarts, the negative rail is at -50 and postive +60.

The voltages really vary dependant upon how many relays switch on after 3 seconds.

[krustyone]

Re: Yamaha RX-A1030 I Protect

Also, I_PRT_L & R are reading 59v.

[R_J]

Re: Yamaha RX-A1030 I Protect

The output voltage on C1106 and C1105 will depend on RY109, The voltage will be low, plus and minus 40 volts untill the relay RY109 cuts in, then the voltage will be plus and minus 60 volts.
If your negative supply is only -50 volts and the positive is +60 volts, you mighthavea bad C1106 or possibly a leaky D1050 bridge

When you say : Also, I_PRT_L & R are reading 59v. do you mean I_PRT_L and I_PRT_R are both positive 59 volts?

[krustyone]

Re: Yamaha RX-A1030 I Protect

Correct. Although they are both linked at intersection B2 on page 152 so what ever the voltage is on one, it will be the same on the other.

[R_J]

Re: Yamaha RX-A1030 I Protect

So you are getting +59 volts on I_PRT_L & R , I would check all the .22Ω emitter resistors, You could also check the voltage on the center of the dual .22Ω It needs to be 0 volts.
Also make sure you has both the B+ and B- voltages going to the amp board.
You either have something shorted on the positive side of the amp, or you have something open on the negative side, causing the center to be offset to the +59 volts

[krustyone]

Re: Yamaha RX-A1030 I Protect

After conducting the checks you suggested and having erratic voltages depending on what relay had kicked in, I decided to cut the power to both each of the amps progressively.

It appears MAIN 1 might be the cause to pull the -B rail down as I still had rails that were different by 10v.
After both amp modules were disconnected, both the -B & +B rails held steady at 55v respective of their relevant polarities.
What I did note was that -LB_R, +LB_R, -LB_L and +LB-L were all missing the -59v as listed at CB106.

After disconnecting both modules from -B and +B, I_PRT_L & R were still showing +59v.

I pulled the amp right down as you cannot get to MAIN 3 without doing so.
I checked C1004, R1014 and Q1005 which they appeared to be ok.

The thing that puzzled me the most is when I check for any shorts with the continuity checker on a Fluke 117, it would beep indicating a short in one direction however when I swapped the leads, there was no short. The meter would also show no short in the ohm settings.

So, it appears there is 2 faults, I_PRT_L & R showing +59v with the supply rails to the amp modules disconnected and a possible issue with MAIN 1.

[R_J]

Re: Yamaha RX-A1030 I Protect

Do you have positive voltage on +LB_R and minus voltage on -LB_R? even if you disconnect the B+ and B- going to the amp these voltages should be there
see page 152, you may have a fault in that supply
Ignore the beep when testing, you need to look at the actual reading, Use diode test to check transistors, diodes etc and regular ohm setting for resistors.

Check the resistors like R1124,R1298, R1093 etc. You likely have something bad in the driver section

[krustyone]

Re: Yamaha RX-A1030 I Protect

Can someone please help me to understand the +LB & -LB supply on page 152 in B5. Both of these voltages are missing.

I found a schematic that utilises the same amp and supply boards as the RX-A1030 that shows test voltages.

After pulling the receiver apart to get to the MAIN board, I disconnected the MAIN 1 & 2 to concentrate on the +LB & -LB supplies that are generated around Q1009 & Q1010 from -B & +B.

I have connected MAIN directly to the transformer which is connected directly to mains.

Both -B & +B come from the bridge rectifier D1050. these voltages are reasonably correct at - & +57 volts respectively.

When I trace the voltage around Q1010, -57v is visible at collector however there is only around -8v on the emitter and base.

I have swapped Q1009 and Q1010 with each other and the same issue occurs. I am also getting a voltage drop across R1286 of 47v however I have swapped the resistor with no change.

C1002 and C1007 check out ok. R1287 tested to be 71k however replacing this also provided no joy. D1063, R1288 and R1008 all tested to be ok.

Only thing I can determine is that Q1010 is switched by Q1098 which in turn is supplied from D1062 etc. Is this correct?

So further to this, is AMP_LMT driving this section to switch the + & - B rails to generate - & + LB? If this is correct, I may have been chasing the wrong fault. i.e. the real fault might be AMP-LMT missing the indicated 3.1v.

[R_J]

Re: Yamaha RX-A1030 I Protect

It looks like the AMP_LMT is the control line for that power supply section, without the 3.1 to turn on Q1096, the +LB & -LB wil be turned off. The AMP_LMT signal comes from the micro
When you first turn on the amp do you have AMP_LMT 3.1 volts on Q1096 base?
when you first turn on the amp do you have +LB voltage but are missing -LB voltage?
The amp_limit line might be missing because the amp detects a fault elsewere and has this voltage turned off to protect the amp outputs. Its hard to tell (chicken/egg)

You seem to have located the fault to the main1, can you isolate the main1 section and connect the rest to see if the amp turns on?

Can you check the offset voltage on the emitters of the outputs when the amp is first turned on, this voltage should indicate which amp section has a fault

[krustyone]

Re: Yamaha RX-A1030 I Protect

Thanks R_J.
I’ll do those checks and report back.

[krustyone]

Re: Yamaha RX-A1030 I Protect

Ok, an update.

The board with the +LB, -LB supplies is impossible to get to with the amp fully assembled.
I can confirm AMP_LMT is producing 3.1v at the digital board.
I can also confirm that -LB is missing in that it is only reading +1.5 however +LB is at +54.6 which based on another schematic I have for the RX-v1067 with the same Main 1, 2 and 3 boards, is normal.
Currently, all speaker outputs are showing +1.2v.

I couldn't find any issues with Main 1 or 2 after checking all voltages and transistors etc apart from the missing -LB_L/R & +LB-L/R in the pre-stages of the amp modules.

I guess the next checks are R1285, D1062, D1063 and Q1098.
I checked and swapped Q1010 and Q1009 so don't believe Q1010 is at fault at this stage.

As I said, It's virtually impossible to check Main 3 when assembled.

My next step would be to apply a simulated 3.1 voltage to the AMP_LMT line with MAIN 3 out of the amp to be able to determine where the failure is.

[R_J]

Re: Yamaha RX-A1030 I Protect

and check R1288, the other problem might be that -LB is being loaded down but I don't see where that could be happening

[hanasaku]

Re: Yamaha RX-A1030 I Protect

Hi , Krustyone, did you found the solution on your RX-A1030? i have the same issue , i check all the signal and the ground are floating with 7.8v all my output have -7.5 volt.

someone can guide me?

regards

[hanasaku]

Re: Yamaha RX-A1030 I Protect

i disconnect the CB106 and CB105 and the voltage are gone, but i presume at the transistors are ok on the amp.

[hanasaku]

Re: Yamaha RX-A1030 I Protect

R_J

Can you help me ? did you find the problem on your receiver?